KR20100036385A - Catalyst layer, membrane electrode assembly and fuel cell - Google Patents

Abstract

Disclosed is a catalyst layer using an electrode catalyst having high oxygen reducing ability, which is useful as a substitute for a platinum catalyst. Also disclosed is a use of such a catalyst layer. Specifically disclosed is a catalyst layer comprising an electrode base and an electrode catalyst formed on the surface of the electrode base and composed of a metal compound which is obtained by hydrolyzing a metal salt or a metal complex.

Description

Catalytic layer, membrane electrode assembly and fuel cell {CATALYST LAYER, MEMBRANE ELECTRODE ASSEMBLY AND FUEL CELL}

The present invention relates to a catalyst layer, a membrane electrode assembly and a fuel cell.

Conventionally, a layer (hereinafter also referred to as a "catalyst layer") containing a catalyst for an electrode (hereinafter also referred to as an "electrode catalyst") has been formed on a cathode (air electrode) surface and an anode (fuel electrode) surface of a fuel cell. .

As this electrode catalyst, a platinum catalyst which is stable at high potential and has high catalytic ability has been used. However, since platinum has a high price and a limited amount of resources, development of a replaceable catalyst has been required.

As an electrode catalyst used for a cathode replacing the platinum catalyst, a metal oxide electrode catalyst has been recently conceived. Metal oxides are generally stable because they do not corrode in acidic electrolytes or in high potentials. In addition, by forming a layer of the electrode catalyst on the surface of the electrode using a metal oxide, the electrode itself can be stably present.

For example, Patent Document 1 (Japanese Patent Laid-Open No. 2004-95263) discloses an electrode catalyst using a metal oxide, including WO ₃ , TiO ₂ , ZrO ₂ , PtO, Sb ₂ O _4, or Sb ₂ O ₃ . A fuel cell catalyst has been proposed. However, the fuel cell catalyst is supposed to use platinum in combination, and there is still room for improvement.

Further, Patent Document 2 (Japanese Patent Laid-Open No. 2005-63677) proposes a fuel cell using ruthenium oxide, titanium oxide, vanadium oxide, manganese oxide, cobalt oxide, nickel oxide, or tungsten oxide as an electrode catalyst. However, the electrode catalyst using these metal oxides has a problem that the oxygen reduction ability is low.

Japanese Patent Laid-Open No. 2004-95263 Japanese Patent Laid-Open No. 2005-63677

The present invention aims to solve the problems in the prior art, and an object of the present invention is to provide a catalyst layer comprising an electrode catalyst having a high oxygen reduction ability, a membrane electrode assembly including the layer, and a fuel cell. It is to offer.

MEANS TO SOLVE THE PROBLEM As a result of earnestly examining in order to solve the problem of the said prior art, it discovered that the electrode catalyst formed from the metal compound obtained by the specific manufacturing method has a high oxygen reduction ability, and can be used suitably for a catalyst layer, The present invention has been accomplished.

This invention relates to the following (1)-(14), for example.

(One)

A catalyst layer comprising an electrode catalyst formed of a metal compound obtained by hydrolyzing a metal salt or a metal complex.

(2)

The catalyst layer according to (1), wherein the metal element constituting the electrode catalyst is one metal element selected from the group consisting of niobium, titanium, tantalum, and zirconium.

(3)

The catalyst layer according to (1), wherein the metal element constituting the electrode catalyst is niobium or titanium.

(4)

The catalyst layer according to any one of (1) to (3), wherein the electrode catalyst is a powder.

(5)

Said metal salt is 1 type of metal salts chosen from the group which consists of a metal alkoxide, a metal carboxylate, and a metal halide, The catalyst layer in any one of (1)-(4) characterized by the above-mentioned.

(6)

BET specific surface area of the said electrode catalyst is the range of 1-1000 m <2> / g, The catalyst layer in any one of (1)-(5) characterized by the above-mentioned.

(7)

The catalyst layer according to any one of (1) to (6), wherein the ionization potential of the electrode catalyst is in the range of 4.9 to 5.5 eV.

(8)

The catalyst layer according to any one of (1) to (7), wherein the electrode catalyst is obtained by disintegrating the metal compound.

(9)

The said electrode catalyst is obtained by heat-processing the said metal compound, The catalyst layer in any one of (1)-(8) characterized by the above-mentioned.

10

In the heat treatment, the heat treatment temperature is 400 to 1200 ° C, the catalyst layer according to (9).

(11)

The catalyst layer according to any one of (1) to (10), further comprising electron conductive particles.

(12)

A membrane electrode assembly having a cathode, an anode, and an electrolyte membrane disposed between the cathode and the anode,

The said cathode has a catalyst layer in any one of (1)-(11), The membrane electrode assembly characterized by the above-mentioned.

(13)

A fuel cell comprising the membrane electrode assembly according to (12).

(14)

It is a solid polymer fuel cell, The fuel cell as described in (13) characterized by the above-mentioned.

The catalyst layer of the present invention contains a specific electrode catalyst, and the electrode catalyst has a high oxygen reducing ability, and is stable even in a high acid condition in an acidic electrolyte because it is difficult to corrode.

1 is a graph evaluating the oxygen reduction ability of the fuel cell electrode 1 of Example 1. FIG.
2 is an XRD spectrum of the electrode catalyst (1) of Example 1. FIG.
3 is a graph evaluating the oxygen reduction ability of the fuel cell electrode 2 of Example 2. FIG.
4 is a graph evaluating the oxygen reduction ability of the fuel cell electrode 3 of Example 3. FIG.
5 is an XRD spectrum of the electrode catalyst (3) of Example 3. FIG.
6 is a graph evaluating the oxygen reduction ability of the fuel cell electrode 4 of Example 4. FIG.
7 is an XRD spectrum of an electrode catalyst of the electrode catalyst (4) of Example 4. FIG.
8 is a graph evaluating the oxygen reduction ability of the fuel cell electrode 5 of Example 5. FIG.
9 is an XRD spectrum of an electrode catalyst of the electrode catalyst (5) of Example 5. FIG.
10 is a graph evaluating the oxygen reduction ability of the fuel cell electrode 6 of Example 6. FIG.
11 is an XRD spectrum of an electrode catalyst of the electrode catalyst 6 of Example 6. FIG.
12 is a graph evaluating the oxygen reduction ability of the fuel cell electrode 7 of Example 7. FIG.
13 is an XRD spectrum of an electrode catalyst of the electrode catalyst 7 of Example 7. FIG.
14 is a graph evaluating the oxygen reduction ability of the fuel cell electrode 8 of Example 8. FIG.
15 is an XRD spectrum of an electrode catalyst of the electrode catalyst 8 of Example 8. FIG.
16 is a graph evaluating the oxygen reduction capacity of the fuel cell electrode 9 of Example 9. FIG.
17 is an XRD spectrum of an electrode catalyst of the electrode catalyst (9) of Example 9. FIG.
18 is a graph evaluating the oxygen reduction ability of the fuel cell electrode of Comparative Example 1. FIG.
19 is an XRD spectrum of an electrode catalyst of Comparative Example 1. FIG.
20 is a graph evaluating the oxygen reduction ability of the fuel cell electrode of Comparative Example 2. FIG.
21 is an XRD spectrum of an electrode catalyst of Comparative Example 2. FIG.
22 is a graph evaluating the oxygen reduction capacity of the fuel cell electrode of Comparative Example 3. FIG.
23 is an XRD spectrum of an electrode catalyst of the electrode catalyst of Comparative Example 3. FIG.
24 is a graph evaluating the oxygen reduction capacity of the fuel cell electrode of Comparative Example 4. FIG.
25 is an XRD spectrum of an electrode catalyst of the electrode catalyst of Comparative Example 4. FIG.
26 is a graph evaluating the oxygen reduction capacity of the fuel cell electrode of Comparative Example 5. FIG.
27 is an XRD spectrum of an electrode catalyst of Comparative Example 5. FIG.
28 is a graph evaluating the oxygen reduction ability of the fuel cell electrode of Comparative Example 6. FIG.
29 is an XRD spectrum of an electrode catalyst of Comparative Example 6. FIG.
30 is a graph evaluating the oxygen reduction capacity of the fuel cell electrode of Comparative Example 7. FIG.
31 is an XRD spectrum of an electrode catalyst of Comparative Example 7.
32 is a diagram showing the ionization potential of the electrode catalyst of the electrode catalyst (1) of Example 1. FIG.

[Catalyst layer]

The catalyst layer of this invention is characterized by including the electrode catalyst formed from the metal compound obtained by hydrolyzing a metal salt or a metal complex.

As a metal element which comprises an electrode catalyst, the transition metal which is easy to express catalytic capability is preferable. Among the transition metals, transition metal elements of the periodic table Group IVa and Va which are electrochemically stable in acidic solution are more preferable, and one transition metal element selected from the group consisting of niobium, titanium, tantalum and zirconium is more preferable. Niobium or titanium is particularly preferable because raw materials are easy to obtain.

As a metal salt or metal complex used by this invention, a metal alkoxide, a metal carboxylate, a metal halide, and a metal acetylacetonate complex are mentioned, for example. Especially, it is preferable to use at least 1 sort (s) of metal salt containing a metal alkoxide, a metal carboxylate, and a metal halide, since it is inexpensive and easy to hydrolyze.

As the metal alkoxide, lower alkoxides such as epoxide, propoxide, isopropoxide, butoxide and isobutoxide are preferable. As the metal carboxylate, lower fatty acid salts such as acetate and propionate are preferable. Moreover, as a metal halide, a chloride is preferable.

The metal compound obtained by hydrolyzing the said metal salt or a metal complex is a metal oxide which has a hydroxyl group on the particle surface normally, and the alkoxy group, carboxylic acid group, etc. which originate in a raw material may remain.

The hydrolysis method is generally a method in which water is easily taken into the particles, and defects are likely to occur on the surface thereof. Since the metal compound obtained by hydrolyzing the said metal salt or a metal complex has a (oxygen) defect formed in the surface, the present inventors estimate that the electrode catalyst formed from a metal compound has high oxygen reduction ability.

(Metal compound)

The metal compound used for this invention is a metal compound obtained by hydrolyzing a metal salt or a metal complex.

As a metal salt or a metal complex, the above-mentioned thing can be used.

There is no restriction | limiting in particular as a method of hydrolyzing the said metal salt or a metal complex, The hydrolysis method of the metal salt or metal complex generally performed is used. The metal compound obtained by the hydrolysis method of this invention is a metal oxide which has a hydroxyl group on the particle surface normally. By controlling the reaction, a metal oxide with many surface defects can be obtained.

For example, when metal alkoxide is used as a raw material, the metal alkoxide is dissolved in a solvent and water is added. When metal carboxylate is used as a raw material, alkaline water is added and performed. As an input method of water, alkali, etc., the method by dripping, a pump, etc. is mentioned. It is preferable to make small amount react, because the specific surface area of the metal compound obtained becomes large.

The reaction is usually carried out by stirring. When it performs stirring, hydrolysis reaction can be performed uniformly and the powdery metal compound which is hard to aggregate is obtained.

The reaction may be performed at room temperature or may be performed by cooling and heating. Heating raises the crystallinity of the metal compound obtained. Moreover, a hydroxyl group detach | desorbs and it becomes easy to be a metal oxide with a defect on a surface, and it is preferable. Cooling is preferable because reaction becomes uniform and the specific surface area of the metal compound obtained becomes large.

In addition, the longer the reaction time, the higher the crystallinity of the obtained metal compound is preferable. However, if the reaction time is long, it is not industrial. Therefore, preferable reaction time is 10 minutes-24 hours, More preferably, they are 30 minutes-12 hours, More preferably, they are 1 hour-8 hours.

In addition, when using a metal alkoxide and a metal carboxylate as a raw material, although the alkoxy group and carboxylic acid group derived from a raw material may remain in the particle | grain surface of the metal compound of this invention depending on reaction conditions, The alkoxy group, carboxylic acid group, etc. derived from a raw material can be removed by making reaction time temperature high, lengthening reaction time, and drying and heat processing mentioned later.

The metal compound obtained as mentioned above is obtained in a slurry state normally. A metal compound can be obtained by performing solid-liquid separation from this slurry.

Although solid-liquid separation is performed by processes, such as sedimentation, concentration, filtration, washing | cleaning, and drying of particle | grains, it is not necessary to perform all the said processes, The process required also depending on the property of a slurry etc. differs. Impurities dissolved in the liquid can be removed by sedimentation, concentration, filtration and washing. A flocculant or a dispersant may be used to change the sedimentation rate or the filtration rate. It is preferable that the said coagulant or dispersing agent can be removed as a gas by evaporation, sublimation, thermal decomposition, or the like. Filtration and washing can remove the solvent, the metal salt dissolved in the solvent, and the hydrolysis by-products of the metal complex.

Although drying is a process of evaporating a solvent, depending on a drying temperature, the hydroxyl group which has on the surface of a particle | grain can be detach | desorbed and it can be set as the metal compound with many surface defects. In addition, depending on the kind of the metal salt and the hydrolysis by-product of the metal complex, some or all amounts of impurities, alkoxy groups, carboxylic acid groups and the like derived from the raw materials can be removed by evaporation, sublimation, pyrolysis, and the like. For drying, methods such as reduced pressure drying, hot air drying, and freeze drying are used. Drying is normally performed at room temperature to 400 degreeC for 1 to 24 hours. There is no restriction | limiting in particular in the drying atmosphere, Usually, it is performed in air | atmosphere, inert gas, or under reduced pressure. In order to detach | desorb the hydroxyl group which has on a particle surface, and to make metal oxide with many surface defects, it is good to dry at 100 degreeC or more, Preferably it is 200 degreeC or more.

(Electrode catalyst)

The electrode catalyst used for this invention is formed from the metal compound obtained by hydrolyzing a metal salt or a metal complex. As an electrode catalyst, the above-mentioned metal compound may be used as it is, the thing which heat-treated the metal compound may be used, the thing which disintegrated the metal compound may be used, and the thing which disintegrated the thing which heat-treated the metal compound may be used.

It is preferable that the said electrode catalyst is a powder. A powder is preferable because it has a large catalyst area and excellent catalyst performance.

It is preferable to disintegrate a metal compound. By pulverizing, an electrode catalyst can be made into finer powder, and an electrode catalyst can be suitably disperse | distributed in the catalyst layer containing an electrode catalyst.

As a method of pulverizing a metal compound, a roll electric mill, a ball mill, a medium stirring mill, an airflow grinder, a mortar, the method by a deliquescent machine, etc. are mentioned, for example, In the point which can make a metal compound more fine, An airflow pulverizer is preferable, and the method by induction is preferable at the point by which small amount processing becomes easy.

The BET specific surface area of the electrode catalyst is preferably 1 to 1000 m 2 / g, more preferably 10 to 100 m 2 / g. When the BET specific surface area is smaller than 1 m 2 / g, the catalyst area is small, and when the BET specific surface area is larger than 1000 m 2 / g, it is easy to aggregate and difficult to handle.

In addition, the value of the BET specific surface area in this invention can be measured with a commercially available BET measuring apparatus, For example, it can measure using the micromeritics Gemini 2360 made from Shimadzu Corporation.

The ionization potential of the electrode catalyst is preferably in the range of 4.9 to 5.5 eV, more preferably in the range of 5.0 to 5.4 eV, still more preferably in the range of 5.1 to 5.3 eV. When the ionization potential of the electrode catalyst is in the above range, the electrode catalyst has a high oxygen reduction capacity. Although the details are unclear, the electrode catalyst having an ionization potential within the above range has a high oxygen reduction ability because the electronic state of the metal compound forming the electrode catalyst becomes a state suitable for oxygen reduction, and the present inventors presume have.

In addition, in this invention, an ionization potential is the value obtained by the measuring method in the Example mentioned later.

It is preferable that the said electrode catalyst is powder in order to raise a catalyst capability as mentioned above.

The particle size of the powder of the electrode catalyst can be obtained from the following equation (1) by converting the powder into a spherical shape from the specific surface area determined by the BET method.

Particle diameter of powder of electrode catalyst: D (μm)

Specific gravity of the powder of the electrode catalyst: ρ (g / cm 3)

BET specific surface area of the powder of the electrode catalyst: S (m 2 / g)

In addition, it is preferable to use what heat-treated the said metal compound as an electrode catalyst.

Although heat processing is performed in order to improve the crystallinity of a metal compound, at the same time, impurities can be removed as a gas by evaporation, sublimation, thermal decomposition, or the like. Moreover, depending on the heat processing temperature, the hydroxyl group, the alkoxy group, the carboxylic acid group derived from a raw material, etc. which have on the surface of a particle | grain can be desorbed, and it can be set as the metal compound with many surface defects. Examples of the impurity that can be removed by this method include a hydrolysis by-product and the like, depending on the type of metal salt or metal complex. Usually, heat processing temperature is performed at 400-1200 degreeC. Moreover, although heat time can be suitably determined according to the metal salt, metal complex used as a raw material, the kind of metal compound, heat processing temperature, and oxygen concentration, it is 10 minutes-5 hours normally. In addition, the heat processing time includes the time of temperature rising and temperature decreasing. There is no restriction | limiting in particular in baking atmosphere, Usually, it is performed in air | atmosphere, inert gas, or under reduced pressure. The higher the firing temperature and the longer the firing time, the higher the crystallinity of the metal compound, but the smaller the specific surface area. Optimum conditions are decided by the balance.

Moreover, depending on the kind of metal compound and heat processing temperature, the valence of the metal element which comprises an electrode catalyst can be made larger than before heat processing. It is preferable to increase the valence because the catalytic ability tends to be improved. For example, when a metal compound is niobium dioxide, it changes into niobium pentoxide by heat-processing about 1000 degreeC.

The oxygen reduction initiation potential measured according to the following measuring method (A) of the electrode catalyst used in the present invention is preferably 0.4 V (vs. NHE) or more based on the reversible hydrogen electrode.

[Measurement Method (A):

It puts in a solvent so that the electrode catalyst disperse | distributed to the carbon which is an electron conductive particle may be 1 weight%, it stirs by ultrasonic waves, and a suspension is obtained. As carbon, carbon black (specific surface area: 100 to 300 m 2 / g) (for example, XC-72 manufactured by Cabot) is used to disperse the electrode catalyst and carbon in a weight ratio of 95: 5. In addition, isopropyl alcohol: water (weight ratio) = 2: 1 is used as a solvent.

30 microliters is extract | collected while applying the ultrasonic wave, and it is dripped rapidly on a glass carbon electrode (diameter: 5.2 mm).

After dripping, it dries at 120 degreeC for 1 hour. By drying, a layer containing the electrode catalyst is formed on the glass carbon electrode.

Subsequently, 10 microliters of what diluted Nafion [Dupont Inc. 5% Nafion solution (DE521)] 10 times with pure water is further dripped. This is dried at 120 ° C. for 1 hour.

In this way, using the obtained electrode, in a sulfuric acid solution of 0.5 mol / dm 3 in an oxygen atmosphere and a nitrogen atmosphere at a temperature of 30 ° C., a reversible hydrogen electrode in the sulfuric acid solution of the above concentration was used as a reference electrode. The potential at which a difference of 0.2 mA / cm &lt; 2 &gt; or more starts to appear in the reduction current in the oxygen atmosphere and the reduction current in the nitrogen atmosphere when the current-potential curve is measured by polarizing at a potential scanning speed of / sec is defined as the oxygen reduction start potential. ]

When the oxygen reduction start potential is less than 0.7 V (vs. NHE), hydrogen peroxide may be generated when the electrode catalyst is used as an electrode catalyst for a cathode of a fuel cell. In addition, the oxygen reduction initiation potential is preferably 0.85 V (vs. NHE) or more, because oxygen is appropriately reduced. The higher the oxygen reduction initiation potential is, the more preferable and there is no upper limit, but the theoretical value is 1.23 V (vs. NHE).

The catalyst layer of the present invention formed using the electrode catalyst is preferably used at an electric potential of 0.4 V (vs. NHE) or higher in an acidic electrolyte, and the upper limit of the electric potential is determined by the stability of the electrode, and the potential at which oxygen is generated. Can be used up to about 1.23V (vs. NHE).

If this potential is less than 0.4 V (vs. NHE), there is no problem at all from the viewpoint of the stability of the metal compound, but oxygen cannot be appropriately reduced, and the usefulness of the membrane electrode assembly included in the fuel cell is insufficient as a catalyst layer.

It is preferable that the catalyst layer of this invention contains an electron conductive particle further. If the electronic conductive particles are further included in the catalyst layer including the electrode catalyst, the reduction current may be increased. In order to generate an electrical contact for inducing an electrochemical reaction to the electron conductive particles and the electrode catalyst, the reduction current can be increased.

The said electron conductive particle is normally used as a support | carrier of an electrode catalyst.

Examples of the electron conductive particles include carbon, conductive polymers, conductive ceramics, metals or conductive inorganic oxides such as tungsten oxide or iridium oxide, and these may be used alone or in combination. In particular, since carbon has a large specific surface area, carbon alone or a mixture of carbon and other electron conductive particles is preferable. The electrode catalyst and the catalyst layer containing carbon can further increase the reduction current.

As carbon, carbon black, graphite, graphite, activated carbon, carbon nanotubes, carbon nanofibers, carbon nanohorns, fullerenes and the like can be used. When the particle diameter of carbon is too small, it becomes difficult to form an electron conduction path, and when too large, the gas diffusivity of a catalyst layer tends to fall or the utilization rate of a catalyst falls, It is preferable that it is the range of 10-1000 nm, It is more preferable that it is the range of 10-100 nm.

The conductive polymer is not particularly limited, but for example, polyacetylene, poly-p-phenylene, polyaniline, polyalkylaniline, polypyrrole, polythiophene, polyindole, poly-1,5-diaminoanthraquinone and polyaminodi Phenyl, poly (o-phenylenediamine), poly (quinolinium) salt, polypyridine, polyquinoxaline, polyphenylquinoxaline and the like. Among these, polypyrrole, polyaniline and polythiophene are preferable, and polypyrrole is more preferable.

When the electron conductive particles are carbon, the weight ratio (electrode catalyst: electron conductive particles) of the electrode catalyst and carbon is preferably 80:20 to 1000: 1.

In addition, the catalyst layer of the present invention usually further contains a polymer electrolyte or a conductive polymer as an electrolyte.

The polymer electrolyte is not particularly limited as long as it is generally used in the catalyst layer. Specifically, polymers doped with inorganic acids such as perfluorocarbon polymers having sulfonic acid groups (for example, Nafion (5% Nafion solution (DE521) from DuPont), hydrocarbon-based high molecular compounds having sulfonic acid groups, phosphoric acid) Examples of the compound include an organic / inorganic hybrid polymer in which a part of the functional group is replaced by a proton conductive functional group, a proton conductor in which the polymer matrix is impregnated with a phosphoric acid solution or a sulfuric acid solution. Among these, Nafion (Dupont's 5% Nafion solution (DE521)) is preferable.

The conductive polymer is not particularly limited, but for example, polyacetylene, poly-p-phenylene, polyaniline, polyalkylaniline, polypyrrole, polythiophene, polyindole, poly-1,5-diaminoanthraquinone and polyaminodi Phenyl, poly (o-phenylenediamine), poly (quinolinium) salt, polypyridine, polyquinoxaline, polyphenylquinoxaline and the like. Among these, polypyrrole, polyaniline and polythiophene are preferable, and polypyrrole is more preferable.

The catalyst layer of the present invention is useful as a catalyst layer (cathode catalyst layer) formed on the cathode of a fuel cell because the catalyst layer has a high oxygen reduction ability and contains an electrode catalyst that is hard to corrode even in a high potential in an acidic electrolyte. In particular, it is used suitably for the catalyst layer formed in the cathode of the membrane electrode assembly with which a solid polymer fuel cell is equipped.

As a method of disperse | distributing the said electrode catalyst on the said electroconductive particle which is a support | carrier, methods, such as airflow dispersion and dispersion in a liquid, are mentioned, for example. Dispersion in a liquid is preferable since the electrode catalyst and the electron conductive particles dispersed in the solvent can be used in the catalyst layer forming step. As dispersion in a liquid, the method by an orifice contraction flow, the method by a rotary shear flow, the method by an ultrasonic wave, etc. are mentioned, for example. The solvent used at the time of dispersion in a liquid does not corrode an electrode catalyst and an electron conductive particle, and if it can disperse, there will be no restriction | limiting in particular, A volatile liquid organic solvent, water, etc. are generally used.

Moreover, when dispersing an electrode catalyst on the said electroconductive particle, you may disperse | distribute the said electrolyte and a dispersing agent simultaneously.

Although there is no restriction | limiting in particular as a formation method of a catalyst layer, For example, the method of apply | coating the suspension containing the said electrode catalyst, electron conductive particle, and electrolyte to the electrolyte membrane or gas diffusion layer mentioned later is mentioned. Examples of the coating method include a dipping method, a screen printing method, a roll coating method, a spray method, and the like. Moreover, the method of forming a catalyst layer in an electrolyte membrane by the transfer method after forming a catalyst layer in a base material by the coating method or the filtration method of the suspension containing the said electrode catalyst, an electron conductive particle, and an electrolyte is mentioned, for example.

[Usage]

The membrane electrode assembly of the present invention is a membrane electrode assembly having a cathode, an anode, and an electrolyte membrane disposed between the cathode and the anode, wherein the cathode has the catalyst layer described above.

As the electrolyte membrane, for example, an electrolyte membrane or a hydrocarbon electrolyte membrane using a perfluorosulfonic acid system or the like is generally used, but a membrane in which a polymer electrolyte is impregnated with a membrane or a porous body in which a polymer electrolyte is impregnated with a polymer electrolyte is filled. Etc. may be used.

The cathode is usually formed of a catalyst layer and a gas diffusion layer.

As the gas diffusion layer, any material can be used as long as it has electron conductivity, high gas diffusivity, and high corrosion resistance, but is generally coated with carbon-based porous materials such as carbon paper and carbon cloth, and stainless steel and corrosion resistant materials for weight reduction. One aluminum foil is used.

Moreover, the fuel cell of this invention is provided with the said membrane electrode assembly. It is characterized by the above-mentioned.

The electrode reaction of the fuel cell takes place at the so-called three-phase interface (electrolyte-electrode catalyst-reaction gas). Fuel cells are classified into several types according to differences in electrolytes and the like, and there are molten carbonate type (MCFC), phosphoric acid type (PAFC), solid oxide type (SOFC), and solid polymer type (PEFC). Especially, it is preferable to use the membrane electrode assembly of this invention for a solid polymer fuel cell.

<Examples>

Although an Example demonstrates this invention further in detail below, this invention is not limited to these Examples.

EXAMPLE 1

(Production of Electrode Catalyst)

5.0 g of titanium (IV) tetrabutoxide and monomer (made by Wako Pure Chemical Industries, Ltd.) were dissolved in 100 ml of ethanol (wako Pure Chemical Industries, Ltd.). While stirring, 1.3 ml of ion-exchanged water was added dropwise. Thereafter, stirring was continued for 1 hour. Filtration under reduced pressure gave solid content. After wash | cleaning solid content with 100 ml of ion-exchange water, it filtered under reduced pressure and obtained solid content. This washing and filtration under reduced pressure were repeated five times.

Solid content was put into the alumina crucible and it dried at 120 degreeC for 1 hour. The obtained titanium oxide (IV) was heat-treated under the following conditions while flowing air at a flow rate of 50 NL / min in an electric furnace (table muffle KDF P90 manufactured by Denken Co., Ltd.).

Temperature rise rate: 20 ℃ / min

Firing temperature: 600 ℃

Firing time (holding time): 2 hours

After the heat treatment, the mixture was naturally cooled to recover 1.2 g of titanium (IV) oxide. Further, the recovered titanium (IV) was caused to be sufficiently pulverized to give an electrode catalyst (1).

(Manufacture of Electrode for Fuel Cell)

The oxygen reduction ability was measured as follows. 0.095 g of the obtained electrode catalyst (1) and 0.005 g of carbon (XC-72 manufactured by Cabot) were added to 10 g of a mixed solution in a weight ratio of isopropyl alcohol: pure water = 2: 1, and the mixture was stirred and suspended by ultrasonic waves. 30 microliters of this were apply | coated to the glass carbon electrode (diameter: 5.2 mm), and it dried at 120 degreeC for 1 hour. 10 μl of a diluted Nafion (Dupont Inc. 5% Nafion solution (DE521)) with 10 times of pure water was further applied, and dried at 120 ° C. for 1 hour to obtain a fuel cell electrode (1).

(Evaluation of Oxygen Reduction Capacity)

The catalytic performance (oxygen reduction capacity) of the fuel cell electrode 1 thus produced was evaluated by the following method.

First, the produced fuel cell electrode 1 was polarized in a sulfuric acid solution of 0.5 mol / dm 3 in an oxygen atmosphere and a nitrogen atmosphere at 30 ° C. and a potential scan rate of 5 mA / sec to measure a current-potential curve. . In that case, the reversible hydrogen electrode in the sulfuric acid solution of the said concentration was made into the reference electrode.

From the measurement results, the potential at which a difference of 0.2 mA / cm &lt; 2 &gt; or more started to appear in the reduction current in the oxygen atmosphere and the reduction current in the nitrogen atmosphere was taken as the oxygen reduction start potential, and the difference between them was taken as the oxygen reduction current.

The catalytic performance (oxygen reduction ability) of the fuel cell electrode 1 produced by this oxygen reduction start potential and oxygen reduction current was evaluated.

In other words, the higher the oxygen reduction initiation potential and the larger the oxygen reduction current, the higher the catalytic capability (oxygen reduction ability) of the fuel cell electrode 1.

1 shows the current-potential curve obtained by the above measurement.

It was found that the electrode 1 for a fuel cell produced in Example 1 had a high oxygen reduction ability at an oxygen reduction initiation potential of 0.8 V (vs. NHE).

(Ionization potential)

The ionization potential of the obtained electrode catalyst (1) was measured using the photoelectron spectroscopy MODEL AC-2 manufactured by Ryuge Geiki. The obtained ionization potential is shown in Table 1. The detailed measuring method is as follows.

The electrode catalyst 1 obtained was spread | covered on the whole surface by the spatula in the ultraviolet irradiation part of the sample stand of the measuring apparatus, and it measured. Under the following measurement conditions, the excitation energy of ultraviolet rays was scanned from 4.5 to 5.7 eV from the lower side to the higher side. Also, depending on the electrode catalyst, the threshold at which photoelectron emission starts may not be found at 4.5 to 5.7 eV. In this case, the measurement range was scanned by changing between a minimum of 3.4 eV and a maximum of 6.2 eV.

Set light quantity: 500㎻

Counting time: 15 seconds

Scan interval: 0.1 eV

At this time, the photoelectrons emitted were measured, and a graph was prepared with standardized photoelectron yield (Yield ^ n) on the vertical axis and excitation energy (eV) on the horizontal axis. The standardized photoelectron yield Yield ^ n herein refers to the n power of the photoelectron yield per unit light amount. The value of n was made into 0.5. The excitation energy until the start of electron emission and the excitation energy after the start of electron emission were measured with the measuring device. The obtained graph is shown in FIG. From the graph, the threshold at which photoelectron emission starts is calculated and the threshold is defined as the ionization potential. The obtained ionization potential is shown in Table 1.

(X-ray diffraction)

The X-ray diffraction of the obtained electrode catalyst (1) was performed using the rotor flex made by Rigaku Denki Co., Ltd .. 2, the XRD spectrum of a sample is shown. It was found that it was titanium oxide of the anatase type.

(BET specific surface area measurement)

The BET specific surface area of the electrode catalyst (1) was measured using the Micromeritics Gemini 2360 made from Shimadzu Corporation.

The specific surface area of the electrode catalyst 1 was 7.3 m 2 / g.

EXAMPLE 2

(Production of Electrode Catalyst)

5.0 g of niobium (IV) 2-ethylhexanoate (made by Wako Pure Chemical Industries, Ltd.) was dissolved in 100 ml of ethanol (wako Pure Chemical Industries, Ltd.). While stirring sufficiently, 11 ml of 25% tetramethylammonium hydroxide diluted 5 times with water was added at the rate of (0.2) ml per minute using the dropping funnel. Thereafter, stirring was continued for 5 hours. Filtration under reduced pressure gave solid content. After wash | cleaning solid content with 100 ml of ion-exchange water, it filtered under reduced pressure and obtained solid content. This washing and filtration were repeated five times.

Solid content was put into the alumina crucible, and it dried at 120 degreeC for 1 hour, and obtained 0.94 g of hydrolyzate. Thereafter, pulverization was sufficiently carried out by induction to obtain an electrode catalyst (2).

(Manufacture of Electrode for Fuel Cell)

A fuel cell electrode 2 was obtained in the same manner as in Example 1 except that the electrode catalyst 2 was used instead of the electrode catalyst 1.

(Evaluation of Oxygen Reduction Capacity)

The oxygen reduction ability was evaluated in the same manner as in Example 1 except that the fuel cell electrode 2 was used instead of the fuel cell electrode 1.

3 shows the current-potential curve obtained by the above measurement.

It was found that the fuel cell electrode 2 produced in Example 2 had a high oxygen reduction capacity at an oxygen reduction initiation potential of 0.9 V (vs. NHE).

(Ionization potential)

The ionization potential was measured in the same manner as in Example 1 except that the electrode catalyst (2) was used instead of the electrode catalyst (1). The obtained ionization potential is shown in Table 1.

(X-ray diffraction)

X-ray diffraction was performed in the same manner as in Example 1 except that the electrode catalyst 2 was used instead of the electrode catalyst 1, but could not be identified as amorphous.

The reaction was estimated to be niobium hydroxide (IV) from the hydrolysis reaction and the yield.

(BET specific surface area measurement)

The BET specific surface area was measured in the same manner as in Example 1 except that the electrode catalyst (2) was used instead of the electrode catalyst (1).

The specific surface area of the electrode catalyst (2) was 21 m 2 / g.

EXAMPLE 3

The electrode catalyst 2 obtained in Example 2 was heat-treated under the following conditions while flowing air at a flow rate of 50 NL / min in an electric furnace (table muffle KDF P90 manufactured by Denken Co., Ltd.).

Temperature rise rate: 20 ℃ / min

Firing temperature: 1000 ℃

Firing time: 2 hours

After heat treatment, natural cooling was performed to recover 1.0 g of niobium pentoxide (V). Further, the recovered niobium pentoxide (V) was sufficiently pulverized to cause the electrode catalyst (3).

(Manufacture of Electrode for Fuel Cell)

A fuel cell electrode 3 was obtained in the same manner as in Example 1 except that the electrode catalyst 3 was used instead of the electrode catalyst 1.

(Evaluation of Oxygen Reduction Capacity)

The oxygen reduction ability was evaluated in the same manner as in Example 1 except that the fuel cell electrode 3 was used instead of the fuel cell electrode 1.

4 shows a current-potential curve obtained by the above measurement.

It was found that the fuel cell electrode 3 produced in Example 3 had a high oxygen reduction capacity at an oxygen reduction initiation potential of 1.0 V (vs. NHE).

(Ionization potential)

The ionization potential was measured in the same manner as in Example 1 except that the electrode catalyst (3) was used instead of the electrode catalyst (1). The obtained ionization potential is shown in Table 1.

(X-ray diffraction)

X-ray diffraction was performed in the same manner as in Example 1 except that the electrode catalyst (3) was used instead of the electrode catalyst (1). 5, the XRD spectrum of a sample is shown. It was found that it was monoclinic niobium pentoxide (V).

(BET specific surface area measurement)

The BET specific surface area was measured in the same manner as in Example 1 except that the electrode catalyst 3 was used instead of the electrode catalyst 1.

The specific surface area of the electrode catalyst 3 was 4.6 m 2 / g.

EXAMPLE 4

The electrode catalyst 2 obtained in Example 2 was heat-treated under the following conditions while flowing air at a flow rate of 50 NL / min in an electric furnace (table muffle KDF P90 manufactured by Denken Co., Ltd.).

Temperature rise rate: 20 ℃ / min

Firing temperature: 800 ℃

Firing time: 2 hours

After heat treatment, natural cooling was performed to recover 1.0 g of niobium oxide. Further, the recovered niobium pentoxide (V) was sufficiently pulverized to cause an electrode catalyst (4).

(Manufacture of Electrode for Fuel Cell)

A fuel cell electrode 4 was obtained in the same manner as in Example 1 except that the electrode catalyst 4 was used instead of the electrode catalyst 1.

(Evaluation of Oxygen Reduction Capacity)

The oxygen reduction ability was evaluated in the same manner as in Example 1 except that the fuel cell electrode 4 was used instead of the fuel cell electrode 1.

6 shows the current-potential curve obtained by the above measurement.

The fuel cell electrode 4 produced in Example 4 was found to exhibit high oxygen reduction capacity with an oxygen reduction initiation potential of 0.9 V (vs. NHE).

(Ionization potential)

The ionization potential was measured in the same manner as in Example 1 except that the electrode catalyst 4 was used instead of the electrode catalyst 1. The obtained ionization potential is shown in Table 1.

(X-ray diffraction)

X-ray diffraction was performed in the same manner as in Example 1 except that the electrode catalyst (4) was used instead of the electrode catalyst (1). In FIG. 7, the XRD spectrum of a sample is shown. It was found that it was a niobium oxide of a tetragonal crystal.

(BET specific surface area measurement)

The BET specific surface area was measured in the same manner as in Example 1 except that the electrode catalyst 4 was used instead of the electrode catalyst 1.

The specific surface area of the electrode catalyst 4 was 5.8 m 2 / g.

[Example 5]

The electrode catalyst 2 obtained in Example 2 was heat-treated under the following conditions while flowing air at a flow rate of 50 NL / min in an electric furnace (table muffle KDF P90 manufactured by Denken Co., Ltd.).

Temperature rise rate: 20 ℃ / min

Firing temperature: 600 ℃

Firing time: 2 hours

After heat treatment, natural cooling was performed to recover 1.0 g of niobium pentoxide (V). Further, the recovered niobium oxide was sufficiently pulverized to induce the electrode catalyst (4).

(Manufacture of Electrode for Fuel Cell)

A fuel cell electrode 5 was obtained in the same manner as in Example 1 except that the electrode catalyst 5 was used instead of the electrode catalyst 1.

(Evaluation of Oxygen Reduction Capacity)

The oxygen reduction ability was evaluated in the same manner as in Example 1 except that the fuel cell electrode 5 was used instead of the fuel cell electrode 1.

8 shows the current-potential curve obtained by the above measurement.

The fuel cell electrode 5 produced in Example 5 was found to exhibit high oxygen reduction capacity with an oxygen reduction initiation potential of 0.8 V (vs. NHE).

(Ionization potential)

The ionization potential was measured in the same manner as in Example 1 except that the electrode catalyst 5 was used instead of the electrode catalyst 1. The obtained ionization potential is shown in Table 1.

(X-ray diffraction)

X-ray diffraction was performed in the same manner as in Example 1 except that the electrode catalyst (5) was used instead of the electrode catalyst (1). 9, the XRD spectrum of a sample is shown. It was found that it was a niobium oxide of a tetragonal crystal.

(BET specific surface area measurement)

The BET specific surface area was measured in the same manner as in Example 1 except that the electrode catalyst 5 was used instead of the electrode catalyst 1.

The specific surface area of the electrode catalyst 5 was 31.4 m 2 / g.

EXAMPLE 6

(Production of Electrode Catalyst)

5.0 g of 85% zirconium (IV) butoxide 1-butanol solution (made by Wako Pure Chemical Industries, Ltd.) was dissolved in 20 ml of ethanol (wako Pure Chemical Industries, Ltd.). While stirring sufficiently, 0.96 ml of water was added using a dropping funnel at a rate of (0.2) ml each minute. Thereafter, stirring was continued for 1 hour. Filtration under reduced pressure gave solid content. After wash | cleaning solid content with 100 ml of ion-exchange water, it filtered under reduced pressure and obtained solid content. This washing and filtration were repeated five times.

Solid content was put into the alumina crucible, and it dried at 120 degreeC for 1 hour, and obtained the hydrolyzate. The obtained hydrolyzate was sufficiently pulverized by induction and heat-treated under the following conditions while flowing air at a flow rate of 50 NL / min in an electric furnace (table muffle KDF P90 manufactured by Denken Co., Ltd.).

Temperature rise rate: 20 ℃ / min

Firing temperature: 1000 ℃

Firing time (holding time): 2 hours

After heat treatment, 1.3 g of zirconium oxide (IV) was recovered by natural cooling. Further, the recovered zirconium oxide was sufficiently pulverized to cause the electrode catalyst (6).

(Evaluation of Oxygen Reduction Capacity)

The oxygen reduction ability was evaluated in the same manner as in Example 1 except that the fuel cell electrode 6 was used instead of the fuel cell electrode 1.

10 shows the current-potential curve obtained by the above measurement.

It was found that the fuel cell electrode 6 produced in Example 6 exhibited high oxygen reduction capacity with an oxygen reduction initiation potential of 0.8 V (vs. NHE).

(Ionization potential)

The ionization potential was measured in the same manner as in Example 1 except that the electrode catalyst 6 was used instead of the electrode catalyst 1. The obtained ionization potential is shown in Table 1.

(X-ray diffraction)

X-ray diffraction was performed in the same manner as in Example 1 except that the electrode catalyst 6 was used instead of the electrode catalyst 1. 11 shows the XRD spectrum of the sample. It was found that it was monoclinic zirconium oxide.

(BET specific surface area measurement)

The BET specific surface area was measured in the same manner as in Example 1 except that the electrode catalyst 6 was used instead of the electrode catalyst 1.

The specific surface area of the electrode catalyst 6 was 6.7 m 2 / g.

EXAMPLE 7

(Production of Electrode Catalyst)

5.0 g of niobium (V) epoxide (manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in 30 ml of ethanol (wako Pure Chemical Industries, Ltd.). While stirring sufficiently, 1.5 ml of water was added at a rate of (0.1) ml each minute using a dropping funnel. Thereafter, stirring was continued for 1 hour. Filtration under reduced pressure gave solid content. After wash | cleaning solid content with 100 ml of ion-exchange water, it filtered under reduced pressure and obtained solid content. This washing and filtration were repeated five times.

Solid content was put into the alumina crucible, and it dried at 120 degreeC for 1 hour, and obtained the hydrolyzate. The obtained hydrolyzate was sufficiently pulverized by induction and heat-treated under the following conditions while flowing air at a flow rate of 50 NL / min in an electric furnace (table muffle KDF P90 manufactured by Denken Co., Ltd.).

Temperature rise rate: 20 ℃ / min

Firing temperature: 800 ℃

Firing time (holding time): 2 hours

After heat treatment, natural cooling was performed to recover 2.1 g of niobium pentoxide (V). Further, the recovered niobium oxide was sufficiently pulverized with the induction to obtain an electrode catalyst (7).

(Evaluation of Oxygen Reduction Capacity)

The oxygen reduction ability was evaluated in the same manner as in Example 1 except that the fuel cell electrode 7 was used instead of the fuel cell electrode 1.

12 shows the current-potential curve obtained by the above measurement.

The fuel cell electrode 7 produced in Example 7 was found to exhibit high oxygen reduction capacity with an oxygen reduction initiation potential of 0.8 V (vs. NHE).

(Ionization potential)

The ionization potential was measured in the same manner as in Example 1 except that the electrode catalyst (7) was used instead of the electrode catalyst (1). The obtained ionization potential is shown in Table 1.

(X-ray diffraction)

X-ray diffraction was performed in the same manner as in Example 1 except that the electrode catalyst (7) was used instead of the electrode catalyst (1). In FIG. 13, the XRD spectrum of a sample is shown. It was found that it was monoclinic niobium oxide.

(BET specific surface area measurement)

The BET specific surface area was measured in the same manner as in Example 1 except that the electrode catalyst 7 was used instead of the electrode catalyst 1.

The specific surface area of the electrode catalyst 7 was 6.3 m 2 / g.

[Example 8]

(Production of Electrode Catalyst)

5.0 g of niobium pentachloride (NbCl ₅ ) (made by Wakoku Yakku) was dissolved in 50 ml of ethanol (made by Wakoku Yakku). With sufficient stirring, 93 ml of 1 mol / l NaOH solution was added at a rate of (0.1) ml each minute using a dropping funnel. Thereafter, stirring was continued for 1 hour. Filtration under reduced pressure gave solid content. After wash | cleaning solid content with 100 ml of ion-exchange water, it filtered under reduced pressure and obtained solid content. This washing and filtration were repeated five times.

Solid content was put into the alumina crucible, and it dried at 120 degreeC for 1 hour, and obtained the hydrolyzate. The obtained hydrolyzate was sufficiently pulverized by induction and heat-treated under the following conditions while flowing air at a flow rate of 50 NL / min in an electric furnace (table muffle KDF P90 manufactured by Denken Co., Ltd.).

Temperature rise rate: 20 ℃ / min

Firing temperature: 800 ℃

Firing time (holding time): 2 hours

After heat treatment, natural cooling was performed to recover 2.4 g of niobium oxide. Further, the recovered niobium oxide was sufficiently pulverized to generate an electrode catalyst (8).

(Evaluation of Oxygen Reduction Capacity)

The oxygen reduction ability was evaluated in the same manner as in Example 1 except that the fuel cell electrode 8 was used instead of the fuel cell electrode 1.

14 shows the current-potential curve obtained by the above measurement.

The fuel cell electrode 8 produced in Example 8 was found to exhibit high oxygen reduction capacity at an oxygen reduction initiation potential of 0.9 V (vs. NHE).

(Ionization potential)

The ionization potential was measured in the same manner as in Example 1 except that the electrode catalyst 8 was used instead of the electrode catalyst 1. The obtained ionization potential is shown in Table 1.

(X-ray diffraction)

X-ray diffraction was performed in the same manner as in Example 1 except that the electrode catalyst 8 was used instead of the electrode catalyst 1. 15 shows the XRD spectrum of the sample. It was found that it was monoclinic niobium oxide.

(BET specific surface area measurement)

The BET specific surface area was measured in the same manner as in Example 1 except that the electrode catalyst 8 was used instead of the electrode catalyst 1.

The specific surface area of the electrode catalyst 8 was 8.5 m 2 / g.

EXAMPLE 9

(Production of Electrode Catalyst)

5.0 g of niobium pentachloride (NbCl ₅ ) (made by Wakoku Yakku) was dissolved in 50 ml of ethanol (made by Wakoku Yakku). With sufficient stirring, 93 ml of 1 mol / l NaOH solution was added at a rate of (0.1) ml each minute using a dropping funnel. Thereafter, stirring was continued for 1 hour. Filtration under reduced pressure gave solid content. After wash | cleaning solid content with 100 ml of ion-exchange water, it filtered under reduced pressure and obtained solid content. This washing and filtration were repeated five times.

Solid content was put into the alumina crucible, and it dried at 120 degreeC for 1 hour, and obtained the hydrolyzate. The obtained hydrolyzate was sufficiently pulverized by induction and heat-treated under the following conditions while flowing air at a flow rate of 50 NL / min in an electric furnace (table muffle KDF P90 manufactured by Denken Co., Ltd.).

Temperature rise rate: 20 ℃ / min

Firing temperature: 600 ℃

Firing time (holding time): 2 hours

After heat treatment, natural cooling was performed to recover 2.4 g of niobium oxide. Further, the recovered niobium oxide was sufficiently pulverized to cause the electrode catalyst (9).

(Evaluation of Oxygen Reduction Capacity)

The oxygen reduction ability was evaluated in the same manner as in Example 1 except that the fuel cell electrode 9 was used instead of the fuel cell electrode 1.

16 shows the current-potential curve obtained by the above measurement.

The fuel cell electrode 9 produced in Example 9 was found to exhibit high oxygen reduction capacity at an oxygen reduction initiation potential of 0.8 V (vs. NHE).

(Ionization potential)

The ionization potential was measured in the same manner as in Example 1 except that the electrode catalyst 9 was used instead of the electrode catalyst 1. The obtained ionization potential is shown in Table 1.

(X-ray diffraction)

X-ray diffraction was performed in the same manner as in Example 1 except that the electrode catalyst 9 was used instead of the electrode catalyst 1. In FIG. 17, the XRD spectrum of a sample is shown. It was found that it was a niobium oxide of a tetragonal crystal.

(BET specific surface area measurement)

The BET specific surface area was measured in the same manner as in Example 1 except that the electrode catalyst 9 was used instead of the electrode catalyst 1.

The specific surface area of the electrode catalyst 9 was 26 m 2 / g.

[Comparative Example 1]

(Production of electrode)

For Example 1, except that the electrocatalyst (1) to the niobium pentoxide (Nb ₂ O ₅₎ of powder (Fig. Gojyun Kagaku claim, purity 99.9%), an electrode was produced in the same manner.

(Evaluation of Oxygen Reduction Capacity)

In the same manner as in Example 1, the oxygen reduction ability was evaluated.

18 shows the current-potential curve obtained by this measurement.

This produced electrode was found to exhibit low oxygen reduction capacity with an oxygen reduction initiation potential of 0.3 V (vs. NHE).

(Ionization potential)

In the same manner as in Example 1, the ionization potential of the powder of niobium pentoxide (Nb ₂ O ₅ ) (a high-density powder, 99.9% purity) was measured. The obtained ionization potential is shown in Table 1.

(X-ray diffraction)

In the same manner as in Example 1, X-ray diffraction was performed on a powder of niobium pentoxide (Nb ₂ O ₅ ) (manufactured by High Chemical, Inc., purity of 99.9%).

In FIG. 19, the XRD spectrum of the indium niobium pentoxide powder (high degree of gauze, purity 99.9%) is shown.

It was found that the niobium pentoxide powder (a high-density Kagaku product, purity 99.9%) was tetragonal.

(BET specific surface area measurement)

In the same manner as in Example 1, the BET specific surface area of niobium pentoxide (Nb ₂ O ₅ ) powder was measured.

The BET specific surface area of the powder of niobium pentoxide (Nb ₂ O ₅ ) was 5.5 m 2 / g.

[Comparative Example 2]

(Production of electrode)

For Example 1, except that the electrocatalyst (1) to the powder (Showa Denko whether or sikki manufactured claim, Super Titania F1) of titanium oxide (TiO _2), an electrode was produced in the same manner.

(Evaluation of Oxygen Reduction Capacity)

In the same manner as in Example 1, the oxygen reduction ability was evaluated.

20 shows the current-potential curve obtained by the above measurement.

This produced electrode was found to exhibit low oxygen reduction capacity with an oxygen reduction initiation potential of 0.3 V (vs. NHE).

(Ionization potential)

In the same manner as in Example 1, the ionization potential of the powder of titanium oxide (TiO ₂ ) (manufactured by Showa Denko Co., Ltd., Super Titania F1) was measured. The obtained ionization potential is shown in Table 1.

(X-ray diffraction)

In the same manner as in Example 1, X-ray diffraction was performed on a powder of titanium oxide (TiO ₂ ) (manufactured by Showa Denko Co., Ltd., Super Titania F1).

In Figure 21, the powder of titanium oxide (TiO ₂₎ (Showa Denko whether or sikki manufactured Claim shows the XRD spectrum of the super-titania F1.

It was found that the powder of titanium oxide (TiO ₂ ) (manufactured by Showa Denko Co., Ltd., Super Titania F1) was a mixture of an anatase body and a rutile body.

(BET specific surface area measurement)

In the same manner as in Example 1, the BET specific surface area of the powder of titanium oxide (TiO ₂ ) was measured.

The BET specific surface area of the powder of titanium oxide (TiO ₂ ) was _{21 m 2} / g.

(Comparative Example 3)

(Production of Metal Oxides)

5.0 g of a titanium tetrachloride (TiCl ₄ ) solution (manufactured by Wako Pure Chemical Industries, Ltd.) was put in a crucible made of alumina, and N ₂ was flown in an electric furnace (table muffle furnace KDF P90 manufactured by Denken Co., Ltd.) at a flow rate of 50 NL / min. Heat treatment at

Temperature rise rate: 20 ℃ / min

Firing temperature: 600 ℃

Firing time: 2 hours

After heat treatment, 1.6 g of titanium oxide was recovered by natural cooling. Further, the recovered titanium oxide was sufficiently pulverized to give a metal oxide electrode catalyst.

(Evaluation of Oxygen Reduction Capacity)

In the same manner as in Example 1, the oxygen reduction ability was evaluated.

22 shows a current-potential curve obtained by the above measurement.

This produced electrode was found to exhibit low oxygen reduction capacity with an oxygen reduction initiation potential of 0.3 V (vs. NHE).

(Ionization potential)

In the same manner as in Example 1, the ionization potential of titanium oxide was measured. The obtained ionization potential is shown in Table 1.

(X-ray diffraction)

In the same manner as in Example 1, X-ray diffraction of titanium oxide was performed.

23 shows the XRD spectrum of titanium oxide.

It was found that the titanium oxide was rutile titanium oxide.

(BET specific surface area measurement)

In the same manner as in Example 1, the BET specific surface area of the titanium oxide powder was measured.

The BET specific surface area of the titanium oxide powder was 9.7 m 2 / g.

(Comparative Example 4)

(Production of Metal Oxides)

In Comparative Example 3, 5.0 g of a titanium tetrachloride (TiCl ₄ ) solution (wakokuyakuje) was made 5.0 g of niobium chloride (NbCl ₅ ) (wakokuyaku) and the firing temperature was set to 1000 ° C instead of 600 ° C. In the same manner, 2.4 g of niobium oxide was recovered. In addition, niobium oxide was pulverized by induction.

(Production of electrode)

In Example 1, the electrode was produced similarly except having made the metal oxide electrode catalyst 1 into the pulverized niobium oxide.

(Evaluation of Oxygen Reduction Capacity)

In the same manner as in Example 1, the oxygen reduction ability was evaluated.

24 shows a current-potential curve obtained by the above measurement.

This produced electrode was found to exhibit low oxygen reduction capacity with an oxygen reduction initiation potential of 0.3 V (vs. NHE).

(Ionization potential)

In the same manner as in Example 1, the ionization potential of niobium oxide was measured. The obtained ionization potential is shown in Table 1.

(X-ray diffraction)

In the same manner as in Example 1, X-ray diffraction of niobium oxide was performed.

25 shows the XRD spectrum of niobium oxide.

Niobium oxide was found to be monoclinic niobium oxide.

(BET specific surface area measurement)

In the same manner as in Example 1, the BET specific surface area of niobium oxide powder was measured.

The BET specific surface area of niobium oxide powder was 1.9 m 2 / g.

(Comparative Example 5)

(Production of Metal Oxides)

In Comparative Example 3, 5.0 g of a titanium tetrachloride (TiCl ₄ ) solution (wakokuyaku) was made 5.0 g of niobium chloride (NbCl ₅ ) (wakokuyaku) and the firing temperature was 800 ° C instead of 600 ° C. In the same manner, 2.4 g of niobium oxide was recovered. In addition, niobium oxide was pulverized by induction.

(Production of electrode)

In Example 1, the electrode was produced similarly except having made the metal oxide electrode catalyst 1 into the pulverized niobium oxide.

(Evaluation of Oxygen Reduction Capacity)

In the same manner as in Example 1, the oxygen reduction ability was evaluated.

26 shows the current-potential curve obtained by the above measurement.

This produced electrode was found to exhibit low oxygen reduction capacity with an oxygen reduction initiation potential of 0.3 V (vs. NHE).

(Ionization potential)

In the same manner as in Example 1, the ionization potential of niobium oxide was measured. The obtained ionization potential is shown in Table 1.

(X-ray diffraction)

In the same manner as in Example 1, X-ray diffraction of niobium oxide was performed.

27, the XRD spectrum of niobium oxide is shown.

Niobium oxide was found to be a tetragonal niobium oxide.

(BET specific surface area measurement)

In the same manner as in Example 1, the BET specific surface area of niobium oxide powder was measured.

The BET specific surface area of niobium oxide powder was 2.9 m 2 / g.

(Comparative Example 6)

(Production of Metal Oxides)

In Comparative Example 3, 2.4 g of niobium oxide was recovered in the same manner except that 5.0 g of a titanium tetrachloride (TiCl ₄ ) solution (wakokukuku) was made 5.0 g of niobium chloride (NbCl ₅ ) (wakokuku). In addition, niobium oxide was pulverized by induction.

(Production of electrode)

In Example 1, the electrode was produced similarly except having made the metal oxide electrode catalyst 1 into the pulverized niobium oxide.

(Evaluation of Oxygen Reduction Capacity)

In the same manner as in Example 1, the oxygen reduction ability was evaluated.

28 shows a current-potential curve obtained by the above measurement.

This produced electrode was found to exhibit low oxygen reduction capacity with an oxygen reduction initiation potential of 0.3 V (vs. NHE).

(Ionization potential)

In the same manner as in Example 1, the ionization potential of niobium oxide was measured. The obtained ionization potential is shown in Table 1.

(X-ray diffraction)

In the same manner as in Example 1, X-ray diffraction of niobium oxide was performed.

29 shows the XRD spectrum of niobium oxide.

Niobium oxide was found to be a mixture of a tetragonal niobium oxide and a monoclinic niobium oxide.

(BET specific surface area measurement)

In the same manner as in Example 1, the BET specific surface area of niobium oxide powder was measured.

The BET specific surface area of niobium oxide powder was 5.1 m 2 / g.

(Comparative Example 7)

(Production of Metal Oxides)

In Comparative Example 3, 5.0 g of titanium tetrachloride (TiCl ₄ ) solution (made by Wako Pure Chemical Industries, Ltd.) was set to 5.0 g of zirconium tetrachloride (ZrCl ₄ ) (made by Wako Pure Chemical Industries), and the firing temperature was changed to 1000 ° C. instead of 600 ° C. In the same manner, 2.6 g of zirconium oxide was recovered. In addition, zirconium oxides were disintegrated by induction.

(Production of electrode)

In Example 1, the electrode was produced similarly except having made the metal oxide electrode catalyst 1 into the above-mentioned disintegrated zirconium oxide.

(Evaluation of Oxygen Reduction Capacity)

In the same manner as in Example 1, the oxygen reduction ability was evaluated.

30 shows a current-potential curve obtained by the above measurement.

This produced electrode was found to exhibit low oxygen reduction capacity with an oxygen reduction initiation potential of 0.3 V (vs. NHE).

(Ionization potential)

In the same manner as in Example 1, the ionization potential of the zirconium oxide was measured. The obtained ionization potential is shown in Table 1.

(X-ray diffraction)

In the same manner as in Example 1, X-ray diffraction of zirconium oxide was performed.

31 shows the XRD spectrum of the zirconium oxide.

It was found that the zirconium oxide is a monoclinic zirconium oxide.

(BET specific surface area measurement)

In the same manner as in Example 1, the BET specific surface area of the zirconium oxide powder was measured.

The BET specific surface area of the zirconium oxide powder was 1.6 m 2 / g.

Claims (14)

A catalyst layer comprising an electrode catalyst formed of a metal compound obtained by hydrolyzing a metal salt or a metal complex. The catalyst layer according to claim 1, wherein the metal element constituting the electrode catalyst is one metal element selected from the group consisting of niobium, titanium, tantalum and zirconium. The catalyst layer according to claim 1, wherein the metal element constituting the electrode catalyst is niobium or titanium. The catalyst layer according to any one of claims 1 to 3, wherein the electrode catalyst is a powder. The catalyst layer according to any one of claims 1 to 4, wherein the metal salt is one metal salt selected from the group consisting of metal alkoxides, metal carboxylates and metal halides. The catalyst layer according to any one of claims 1 to 5, wherein the BET specific surface area of the electrode catalyst is in the range of 1 to 1000 m 2 / g. The catalyst layer according to any one of claims 1 to 6, wherein the ionization potential of the electrode catalyst is in the range of 4.9 to 5.5 eV. The catalyst layer according to any one of claims 1 to 7, wherein the electrode catalyst is obtained by disintegrating the metal compound. The catalyst layer according to any one of claims 1 to 8, wherein the electrode catalyst is obtained by heat treatment of the metal compound. The catalyst layer according to claim 9, wherein in the heat treatment, the heat treatment temperature is 400 to 1200 ° C. The catalyst layer according to any one of claims 1 to 10, further comprising electron conductive particles. A membrane electrode assembly having a cathode, an anode, and an electrolyte membrane disposed between the cathode and the anode,
The said cathode has the catalyst layer in any one of Claims 1-11, The membrane electrode assembly characterized by the above-mentioned. A fuel cell comprising the membrane electrode assembly according to claim 12. The fuel cell according to claim 13, wherein the fuel cell is a solid polymer fuel cell.

Images